Abstract
Thrombus formation, despite efficient anticoagulation with heparin, takes place on the dialyzer membrane during hemodialysis. Since thrombus formation is associated with a transient fall in platelet count and an elevation of platelet factor 4 (PF4), it is hypothesized that platelet retention on these membranes is an initial step in the process leading to thrombus formation. To determine whether aspirin reduces this thrombus formation on the dialyzer, the platelet counts and PF4 levels and mean platelet volumes (MPV) during hemodialysis with the patient taking 1gm of aspirin daily were compared with the levels during a control period without aspirin. At first, to assess the direct effect of heparin on platelet activation, heparin (5, 000u) was injected in to a normal control intravenously as a bolus.
A transient fall in platelet count and an elevation of PF4 were seen 15 minutes after the injection and were rapidly cleared by the circulation. One gm of aspirin per os with heparin has been shown to reduce the elevation of PF4 significantly. Similarly during hemodialysis, a transient fall in platelet count and an elevation of PF4 were seen, especially 30 minutes after the beginning, but 1gm of aspirin with heparin could not suppress the elevation of PF4, Therefore it was concluded that the platelet activation during hemodialysis was due not only to the blood-dialyzer surface interaction but also to the direct effect of heparin itself. Furthermore 1gm of aspirin reduced the platelet activation caused by heparin itself but did not reduce the activation during hemodialysis with heparin as an anticoagulant.
